BAGHDAD, Iraq - The day seemed tranquil at Muqtada Sadr's headquarters for western Baghdad. Pigeons flew overhead, swooping down to perch on palm trees that dotted the courtyard. Uniformed Iraqi police officers and soldiers sipped tea with rugged militiamen or exchanged customary kisses with black-turbaned clerics. Women came to plead for assistance.

But calm is always fleeting in Baghdad. At midday, about 50 gunmen stormed the courtyard and ordered everyone inside to stay put and to stay silent.

Sadr's Mahdi Army militiamen responded immediately, drawing automatic rifles and pistols from under their winter coats and gathering in a cluster to face the unidentified gunmen. The assailants closed ranks, brandishing shiny revolvers and battered machine guns.

The groups walked toward each other as if in a high-noon duel. A voice from the crowd called for blessings in the name of Islam's Prophet Muhammad. Sadr's soldiers began to shout age-old prayers for the prophet and his descendants, then added the Sadr camp's innovation: "Bring salvation soon, and damn their enemies!"

With the air filled with the clicking sound of weapons being prepared, visiting McClatchy journalists fled.

The sudden intrusion of the gunmen into one of Sadr's most secure strongholds exposed a paradox that dogs the Sadr movement and contributes to the daily bloodletting here: The Mahdi Army is growing larger and more sophisticated, with politicians in the government and a vast social services network that serves thousands of poor Shiites, but the anarchy of the streets makes it hard for the militia's commanders to rein in their men, much less prevent attacks from rival factions.

Even as Sadr presses for more land and power, his grasp over Baghdad remains tenuous...........................These days, the safest route to Sadr's west Baghdad office runs through an obstacle course of both legal and dubious checkpoints in an area known for kidnappings and car bombings.

On Tuesday, there were eight: The first was an imposing roadblock manned by Iraqi army soldiers in camouflage. The next four were guarded by Iraqi police in mismatched uniforms. Then came a couple of apparent militiamen standing in the street with guns, and next, a vehicle search by more plainclothes sentries. Finally, another batch of unidentified guards stopped pedestrians at a coil of razor wire to peer into women's bags and pat down men for weapons.

Gone are the peaceful seminary days. In their place, men in long overcoats hover, casting steely glares on anyone who enters the compound. The courtyard brims with new faces and dialects. Some were distraught Iraqis seeking financial or security help; others were militiamen or workers from Sadr's social programs.

A large poster hung on the wall showing Sadr, the firebrand cleric-turned-commander, alongside fellow Shiite Muslim leader Hassan Nasrallah, head of Lebanon's Hezbollah. Sadr stood on an American flag; Nasrallah on an Israeli one. The caption read: "Their arrogance is under your feet."

An elderly blue-eyed woman shuffled in and beseeched Sadr's representatives for medical assistance for her three sons. Two of them had been shot by U.S. troops, she said, and the third had fallen off a motorcycle while fighting Sunni gunmen.

"Are they in the imam's army?" a tall, stern man asked.

"Yes, they all are," the woman replied.

"OK, just give me their names and papers and we'll sponsor them," he said.

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"If we talk about the word 'militia,' the Mahdi Army doesn't fit the description. We are a group of people with a belief," said Araji, now national director of Sadr's social programs and a local militia commander. "We call it an army, but it's not just an army of gunmen. We protect our neighborhoods and provide services for our people."

Araji said he had visited Lebanon and Iran recently to check on the welfare of Iraqis in prisons and refugee camps. When asked whether he had met with Hezbollah chief Nasrallah in Lebanon, he smiled, shook his head and steered the conversation back to his two trips to Iran. On those jaunts, he evaluated the needs of 90,000 Iraqis in exile.

At home, he said, his time is consumed with the displacement of tens of thousands of Iraqis in what he called "one of the biggest crises in modern history."

When told that Sunni Web sites accused him of fielding death squads, Araji scoffed.

"Let them bring proof," he said. "We still have many Sunni families in Kadhemiya. No one has been displaced here, but in the hot spots of Karkh, of course, there are problems. It's the same for Sunnis and Shiites." Karkh is how residents of Baghdad refer to the largely Sunni side of the city that lies west of the Tigris River.

'Weak government'

Araji said the government had failed so miserably in providing basic services that his office petitioned the local council six months ago to take over the distribution of cooking gas and other supplies. Now, he said with pride, the Mahdi Army delivers gas and kerosene to families throughout Kadhemiya and other heavily Shiite districts.

Funding for the projects, he said, comes mainly from 2,000 donation boxes throughout Iraq that are stuffed with cash every week after Friday prayers.

"It's a weak government," he said. "They're supposed to do this, but we do it."

Araji said the Mahdi Army doesn't seek to replace the Iraqi government, but that it's obligated to step in until elected officials show results.

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Five minutes later, the gunmen arrived. Araji's black turban was lost in a tangle of uniformed and plainclothes gunmen, the swish of black robes as women ran for cover, and the glint of sunshine on weapons.

In a phone call later that night, he dismissed the showdown as "a tribal matter" and emphasized that no one was injured. Kadhemiya was still safe.

"It was a private matter," he said, and offered no further explanation